Principle of Operation

Principle of operation
Program-controlled four-speed automatic transmission

AW 30-40 and AW 30-43 are four-speed units with a torque converter lock-up function in the three highest gears. In addition to the gear selector lever, the transmission is provided with a driving mode selector (1) offering a choice of three different driving modes. The gearshifting and lock-up functions are both controlled by the TCM (2), which is supplied with signals by the gear position sensor (3) and the driving mode selector, among other devices.
The TCM also uses information from the engine electronic management system and the speedometer.

Troubleshooting with on-board diagnostics (OBD)

To facilitate troubleshooting, the TCM is provided with an integral diagnostic function which enables control system faults to be detected and subsequently displayed, using either the LED on the data link connector (DLC) (4) or the Volvo ST.

In the event of a serious fault, a special emergency program is activated to enable the car to be driven to the nearest workshop, the fault being indicated by flashing of a malfunction indicator lamp (Mil) (5) on the combined instrument.

TCM

All information is processed by the TCM, which computes the gearshifting and lock-up engagement points according to the driving mode selected. The TCM then performs gearshifting and lock-up engagement electrically by means of the integral solenoid valves (S1, S2, SL and STH), which operate the transmission hydraulics in the same manner as in earlier mechano-hydraulic automatic transmissions.

Shift lock

The gear selector mechanism is equipped with an electronic shift lock function to prevent inadvertent engagement of the wrong gear. Shift lock prevents the gear lever from being moved from the parking (P) position unless the brake is applied and the ignition is switched on.
This function is included only in certain markets.





Exterior

The mechanical and hydraulic components of the transmission are contained in the torque converter housing (8), transmission housing (9), rear extension housing (10) and oil pan (11).

The speed sensor (12) in the front transmission housing, temperature sensor (13) in the oil cooler outlet, gear position sensor (5) on the gear selector shaft (14) and the solenoid valves in the control system are wired to three connectors (15).

The gear position sensor also incorporates a reversing light switch and a start inhibit switch which make it impossible to start the engine unless the gear selector lever is in position P or N.

Cooled fluid from the cooler is returned to the transmission through the inlet (17). The oil cooler is integral with the ordinary radiator and cannot be replaced separately.
The TCM receives information regarding the speed of the front planetary sun wheel from a sensor (12) installed in the front section of the transmission housing.
The fluid is checked and topped up through the dipstick tube (18).